1. Field of the Invention
This invention relates to a communication apparatus, and more particularly to a communication apparatus for carrying out data communication between a data terminal equipment and a controlled equipment using a radio wave.
2. Discussion of the Background
Various types of data communication have been conventionally carried out using a radio wave between a controlled equipment and a data terminal equipment. In this instance, a communication apparatus is provided for each of the controlled equipment and data terminal equipment.
Now, such a conventional communication apparatus will be described with reference to FIG. 4. A communication apparatus generally designated at reference numeral 100 in FIG. 4 includes an input terminal for a data terminal equipment (DTE input terminal) designated at reference numeral 101 which is adapted to receive input data from a data terminal equipment (DTE) (not shown) and a central processing unit (CPU) 103 for carrying out control of the whole communication unit 100.
The CPU 103 is provided therein with a read only memory (ROM) 104a for storing a variety of programs therein and a random access memory (RAM) 104b in which input data inputted through the DTE input terminal 101 to the CPU 103 are temporarily stored. Also, the CPU 103 has a predetermined operation clock inputted thereto from a clock generator.
The communication unit 100 also includes a command analysis processing block 106 which functions to subject a command transmitted thereto through a bus line to analysis processing and transfer results of the analysis processing to the CPU 103.
Reference numeral 107 designates an RF control block which functions to subject command data transmitted through a bus line thereto to control of various types. For example, the RF control block 107 controls an RF modem or modulator demodulator 108 acting as a data circuit terminating equipment and a phase locked loop (PLL) circuit section 109b arranged in an RF circuit section 109a. 
As data to be transmitted to a controlled equipment (not shown) through a bus line, transmission data in the form of a predetermined signal are prepared, for example, when command data, text data or the like are transmitted.
The RF modem block 108 modifies transmission data transmitted from the RF control block 107 through a bus line thereto according to a predetermined modulation system and then outputs it in the form of a base band signal (DC digital signal).
In the RF circuit section 109a, a predetermined transmission channel is selected from predetermined plural transmission channels by the PLL circuit section 109b. Also, the RF circuit section 109a converts a base band signal (digital signal) fed from the RF modem block 108 thereto into an analog data signal. Further, the RF circuit section 109a modifies a carrier by means of the analog data signal and transmits it from an antenna 120 through an antenna terminal 110.
In the conventional communication unit 100 shown in FIG. 4, a digital processing block constituted by, for example, the CPU 103, command analysis processing block 106, RF control block 107 and RF modem block 108 surrounded by broken lines in FIG. 4 is normally constituted by a one-chip microcomputer 102. In this instance, operation of the one-chip microcomputer 102 is controlled by a single operation clock fCK, so that an operation clock for the one-chip microcomputer 102 is set at a highly increased operation speed which permits processing required in each of the processing blocks to be attained.
It is generally known that electric power consumed by an integrated circuit (IC) such as a microcomputer or the like is determined depending on a gate size of the IC and an operation clock therefor. For example, when power consumption of the IC, the gate size and the operation clock are indicated at P, Gs and fCK, respectively, power consumption P of the IC is represented by the following expression:
P=Gsxc3x97fCKxc3x97k
wherein k is a constant. Thus, the integrated circuit is increased in power consumption with an increase in speed of the operation clock fCK.
Therefore, the one-chip microcomputer 102 in which an operation clock increased in speed is fed even to a processing block operable at a low speed has a disadvantage of being increased in whole power consumption.
In particular, in the conventional communication unit 100 described above, an operation clock for the command analysis processing block 106 is set to be 20 kHz, whereas an operation clock for the RF modem block 108 is set at a level as high as 1.1 MHz. Thus, for example, conformation or correspondence of an operation speed of the one-chip microcomputer 102 to that of the RF modem block 108 leads to waste power consumption, because a high-speed clock is used as a whole.
The present invention has been made in view of the foregoing disadvantage of the prior art.
Accordingly, it is an object of the present invention to provide a communication apparatus which is capable of being significantly reduced in power consumption.
In accordance with the present invention, a communication apparatus is provided. The communication apparatus includes a data input terminal for receiving a command outputted from a data terminal unit, a command analysis processing section for subjecting the command inputted thereto through the data input terminal to analysis processing, a control section for carrying out required control depending on command data analyzed in the command analysis processing section, command data to be transmitted of command data analyzed in the command analysis processing section, and an RF transmission section for transmitting transmit data in the form of a predetermined signal. At least the command analysis processing section is constituted by a logic circuit operated by a predetermined clock signal.
As described above, in the present invention, at least the command analysis processing section is constituted by a logic circuit and a low-speed clock signal is fed to the command analysis processing section for operation thereof. Thus, the communication apparatus of the present invention eliminates waste power consumption caused by the conventional command analysis block, leading to a reduction in power consumption.